1. Field of the Invention
The present invention relates to Class AB push-pull amplifier arrangements.
2. Description of the Related Art
Control of the quiescent bias of an output stage of a push-pull Class B amplifier is critical to the amplifier's performance, as it directly influences its crossover distortion and efficiency.
The turn-on voltage of output stage devices typically varies from device to device, and also varies with temperature. The magnitude of the variation is technology dependent, and is particularly large for low cost, high power devices such as MOS switching FETs.
Typically, factory calibration and open loop temperature compensation techniques are used to control the quiescent bias in order to minimise crossover distortion, but for some device classes such techniques are not sufficiently accurate.
The aim of the invention is to provide closed loop control of an output stage quiescent bias by detecting the quiescent current.